This invention relates to a communication system in a system which includes a plurality of communication methods, and more particularly, to a system for selecting a communication method.
In cellular communication, a terminal generally has a sleep mechanism for suppressing power supply consumption by keeping, when not engaged in communication, only minimum necessary functions active while supplying no power supply to the other portions. In a sleep status, the cellular terminal starts a receiver only at a timing when a cellular base station periodically transmits information called paging to check presence of communication.
One of the methods for setting a wireless system usable by the conventional terminal is a method of detecting electric waves emitted from the base station. According to this method, frequencies possibly used by the base station are sequentially searched to detect communicable frequencies, thereby setting a base station to which communication is performed.
A technology of setting a base station based on a positioning result of a terminal position (e.g., JP 2005-80071 A) is available. FIG. 16 illustrates an operation of this technology. According to this technology, upon generation of a communication request 935, whether a terminal is located in a wireless LAN area is searched for from a map recording the wireless LAN area which has been held in the terminal based on a positioning result of a GPS receiver (936). If the terminal is located in the wireless LAN area, communication is tried through a wireless LAN.
A technology of notifying information regarding an area where a wireless LAN can be used from a base station, and trying use of the wireless LAN if a terminal is in the area (e.g., JP 2007-49645 A) is available. FIG. 17 illustrates an operation of this technology. According to this technology, the base station notifies information on whether a wireless LAN access point is present in each area (937). The terminal obtains information on an area where the terminal is present from the notified information, and conducts hand over to the wireless LAN if the wireless LAN can be used (939). Thereafter, in this area, communication is carried out by using the wireless LAN (938).